That’s why you use a NTS + a snitch, it picks replaces based on rack awareness.
> On Feb 20, 2018, at 9:33 AM, Carl Mueller <carl.muel...@smartthings.com> > wrote: > > So in theory, one could double a cluster by: > > 1) moving snapshots of each node to a new node. > 2) for each snapshot moved, figure out the primary range of the new node by > taking the old node's primary range token and calculating the midpoint value > between that and the next primary range start token > 3) the RFs should be preserved since the snapshot have a replicated set of > data for the old primary range, the next primary has a RF already, and so > does the n+1 primary range already > > data distribution will be the same as the old primary range distirubtion. > > Then nodetool clean and repair would get rid of old data ranges not needed > anymore. > > In practice, is this possible? I have heard Priam can double clusters and > they do not use vnodes. I am assuming they do a similar approach but they > only have to calculate single tokens? > > On Tue, Feb 20, 2018 at 11:21 AM, Carl Mueller <carl.muel...@smartthings.com > <mailto:carl.muel...@smartthings.com>> wrote: > As I understand it: Replicas of data are replicated to the next primary range > owner. > > As tokens are randomly generated (at least in 2.1.x that I am on), can't we > have this situation: > > Say we have RF3, but the tokens happen to line up where: > > NodeA handles 0-10 > NodeB handles 11-20 > NodeA handlea 21-30 > NodeB handles 31-40 > NodeC handles 40-50 > > The key aspect of that is that the random assignment of primary range vnode > tokens has resulted in NodeA and NodeB being the primaries for four adjacent > primary ranges. > > IF RF is replicated by going to the next adjacent nodes in the primary range, > and we are, say RF3, then B will have a replica of A, and then the THIRD > REPLICA IS BACK ON A. > > Is the RF distribution durable to this by ignoring the reappearance of A and > then cycling through until a unique node (NodeC) is encountered, and then > that becomes the third replica? > > > >
